UC-NRLF 


'ABASH  1C  / 


RILEV 


893 


yiufl  J1J5V 


ENTOMOLOGY 
LIBRARY 


PARASITIC  AND  I'KKDACEUl* 


INSECTS 


IN 


APPLIED  ENTOMOLOGY 


C.  V.  RILEY,  Ph.  D. 


[  READ  AT  THE  FIFTH  ANNUAL  MEETING  OF  THE  ASSOCIATION  OF 

ECONOMIC  ENTOMOLOGISTS,  MADISON,  WIS.,  AUGUST  15,  1893, 

AND  REPRINTED  FROM  1XHEGT  LIFK,  VOL.  VI,  NO.  .'. 


AVASIIINdTOX: 

GOVERNMENT    1»  II  IN  TING    OFFICE. 

1893. 


PARASITIC  AND  PREDACEOUS 


INSECTS 


IN 


APPLIED   ENTOMOLOGY 


BY 


C.  V.  KILEY,  Ph.  D, 

\\ 


[READ  AT  THE  FIFTH  ANNUAL  MEETING  OF  THE  ASSOCIATION  OF 

ECONOMIC  ENTOMOLOGISTS,  MADISON,  WIS.,  AUGUST  15,  1893, 

AND  REPRINTED  FROM  INSECT  LIFE,  VOL.  VI,  NO.  2. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 

1893. 


ENTOMOLOG/f 
LIBRARY 


[Reprinted  from  tin-  Proceedings  of  the  5th  Annual  Meeting  of  the  Association  of 
Economic  Entomologists,  held  in  Madison,  Wis.,  August  15,  1893,  and  published 
in  Insect  Life,  Vol.  vi,  No.  2.] 

PARASITIC  AND  PREDACEOUS  INSECTS  IN  APPLIED  ENTOMOLOGY. 

By  C.  V.  RILEY.  Washington,  D.  C. 

The  importance  to  man,  and  especially  to  the  agriculturist,  of  the 
parasitic  and  predaceous  insect  enemies  of  such  species  as  injure  veg- 
etation, has  been  recognized  by  almost  all  writers  on  economic  ento- 
mology. Indeed,  it  is  a  question  whether  the  earlier  writers  did  not 
attach  too  much  importance  to  them ;  because,  while  in  the  abstract 
they  are  all  essential  to  keep  the  plant-feeding  species  in  proper  check, 
and  without  them  these  last  would  unquestionably  be  far  more  difficult 
to  manage,  yet  in  the  long  run  our  worst  insect  enemies  are  not  mate- 
rially affected  by  them,  and  the  cases  where  we  can  artificially  encourage 
the  multiplication  of  the  beneficial  species  are  relatively  few.  While 
fully  appreciating  the  importance  of  the  subject,  therefore,  it  is  my  pur- 
pose in  this  paper  to  point  out  the  dangers  and  disadvantages  result- 
ing from  false  and  exaggerated  notions  upon  it. 

There  are  but  two  methods  by  which  these  insect  friends  of  the 
farmer  can  be  effectually  utilized  or  encouraged,  as,  for  the  most  part, 
they  perform  their  work  unseen  and  unheeded  by  him,  and  are  practi- 
cally beyond  his  control.  These  methods  consist  in  the  intelligent  pro- 
tection of  those  species  which  already  exist  in  a  given  locality,  and  in 
the  introduction  of  desirable  species  which  do  not  already  exist  there. 

The  first  method  offers  comparatively  few  opportunities  where  the 
husbandman  can  accomplish  much  to  his  advantage.  That  a  knowledge 
of  the  characteristics  of  these  natural  enemies  may,  in  some  instances, 
be  easily  given  to  him,  and  will,  in  such  instances,  prove  of  material 
value,  will  hardly  be  denied.  The  oft-quoted  experience  which  Dr. 
Asa  Fitch  recorded,  of  the  man  who  complained  that  his  rosebushes 
were  more  seriously  affected  with  aphides  than  those  of  his  neighbors, 
notwithstanding  he  conscientiously  cleaned  off  all  the  old  parent  bugs 
(he  having  mistaken  the  beneficial  ladybirds  for  the  parent  aphides) 
may  be  mentioned  in  this  connection.  Other  cases  will  recur  to  you 
and  I  will  mention  one  rather  striking  experience  related  by  my  assist- 
ant, Mr.  L."  O.  Howard.  The  Army  Worm  (Leucania  unipuncta)  was 
overrunning  a  large  and  valuable  field  of  timothy  and  threatened  the 
destruction  of  the  adjoining  fields.  The  insect  was  as  yet,  however, 
circumscribed,  and  susceptible  of  remedial  treatment.  The  owner  of 
the  field,  observing  the  buzzing  swarms  of  the  Ked-tailed  Tachina-fiy, 
assumed  that  the  fly  was  the  parent  of  the  worms,  and  as  the  former 

274382 


131 

was  an  active,  wrngeVl  mature,  capable  of  extended  flight,  lie  con- 
cluded that  remedial  work  was  useless,  since  the  flies  could,  and  doubt- 
less -would,  deposit  their  eggs  over  the  entire  surrounding  country. 
As  a  consequence  the  worms  were  allowed  to  travel  to  the  adjoining 
fields  and  the  injury  thus  increased  through  ignorance  of  the  fact  that 
the  Tachina  flies  were  the  most  important  of  the  parasitic  enemies  of 
the  worm.  For  many  years  well-informed  gardejiers  in  parts  of  Europe 
have  practiced  collecting  ladybirds  and  some  of  the  ground  beetles  to 
liberate  upon  plants  infested  by  plant-lice  or  by  cutworms.  The  char- 
acteristics of  these  two  families,  Coccinellidae  and'  Carabidse,  should  be 
taught  in  our  schools,  as  a  definite  knowledge  of  certain  species,  which 
is  readily  acquired,  may  often  be  turned  to  account  in  a  limited  way  by 
the  cultivator. 

In  a  few  cases  like  this  there  is  no  reason  why  the  farmer  should  not 
be  taught  with  advantage  to  discriminate  between  his  friends  and  his 
foes,  and  to  encourage  the  multiplication  of  the  former;  but  for  the 
most  part  the  nicer  discriminations  as  to  the  beneficial  species,  some 
of  the  most  important  of  which  are  microscopically  small,  must  be  left 
to  the  trained  entomologist.  Few  of  the  men  practically  engaged  in 
agriculture  and  horticulture  can  follow  the  more  or  less  technical 
characterizations  of  these  beneficial  species,  and  where  the  discrimi- 
nating knowledge  is  possessed  it  can,  as  just  intimated,  only  excep- 
tionally be  turned  to  practical  account.  Thus  our  literature  on  this 
subject  in  the  past  has  been  of  interest  from  the  entomological  rather 
than  from  the  agricultural  point  of  view,  as  most  writers  on  economic 
entomology  have  contented  themselves  with  describing  and  illustrating 
such  beneficial  species. 

In  other  cases  much  good  may  be  done  without  any  special  knowl- 
edge of  the  beneficial  forms,  but  as  a  result  of  a  knowledge  of  the 
special  facts  which  enables  the  farmer  to  materially  encourage  the  mul- 
tiplication of  parasitic  species  while  destroying  the  plant- feeding  host. 

The  Rascal  Leaf-crumpler  (Mineola  indiginella  Z.),  a  common  insect 
which  disfigures  and  does  much  damage  to  our  apple  and  other  fruit 
trees  and  which  hibernates  in  cases  attached  to  twigs,  is  a  case  in 
point.  Many  years  ago  I  urged  the  importance  of  preserving  the  sev- 
eral parasites  known  to  prey  upon  it,  in  the  following  language:* 

The  orchardist  has  but  to  bear  in  mind  that  it  (the  leaf-crumpler)  is  single- 
brooded  and  that  it  passes  the  winter  in  its  case,  and  he  will  understand  that  by 
collecting  and  destroying  these  cases  in  the  dead  of  the  year  when  the  tree  is  bare, 
he  effectually  puts  a  stop  to  its  increase.  *  *  *  Whether  collected  in  winter  or 
pulled  off  the  trees  in  spring  or  summer,  these  cases  should  always  be  thrown  into 
some  small  vessel  and  deposited  in  the  center  of  a  meadow  or  field  away  from  any 
fruit  trees.  Here  the  worms  will  wander  about  a  few  yards  and  soon  die  from 
exhaustion  and  want  of  food,  while  such  of  the  parasites,  hereafter  mentioned,  as 
are  developed  or  in  the  pupa  state  will  mature  and  eventually  fly  off.  In  this 
manner,  as  did  Spartacus  of  old,  we  swell  the  ranks  of  our  friends  while  defeating 
our  foes. 

*Fourth  Report,  Insects  of  Missouri,  1871,  p.  40. 


132 

The  practical  value  of  this  suggestion  was  subsequently  fully  dem- 
onstrated, and  especially  by  the  late  D.  B.  Wier.  who,  at  a  meeting  of 
the  Illinois  Horticultural  Society,  as  secretary  of  a  committee  appointed 
by  said  society  to  consider  the  best  means  of  securing  cooperation  in 
the  warfare  against  the  fruit-growers'  insect  enemies,  announced  that 
this  policy  had  been  followed  with  happy  results. 

A  similar  course  was  urged  by  me  in  the  case  of  our  common  Bag- 
worm  (Thyridopteryx  ephemercvformis).  This  species,  as  we  know,  is 
also  subject  to  parasites,  and  the  bags  or  cases  which  are  collected  in 
winter,  instead  of  being  burned,  should  be  allowed  to  remain  until  the 
middle  of  the  next  summer  in  some  vessel  well  separated  from  trees  and 
shrubs,  in  order  that  the  young  worms,  when  they  hatch  in  spring  from 
the  eggs  contain  d  in  the  female  bag,  may  perish,  while  the  parasites 
develop  and  escape.  Prof.  J.  H.  Comstock  has  suggested  in  a  similar 
way  the  placing  of  the  hand-collected  chrysalides  of  the  imported  Cab- 
bage Worm  (Pieris  rupee)  in  boxes  covered  with  wire  netting,  in  order 
to  admit  of  the  ready  escape  of  the  little  (Jhalcid  parasite  (Pteromalus 
puparum)  and  at  the  same  time  retain  such  of  the  butterflies  as  may 
issue — a  practice  which  had,  I  believe,  been  successfully  employed  in 
Europe.  Other  similar  cases  of  this  mode  of  encouragement  will  occur 
to  you,  but,  as  already  stated,  with  comparatively  few  exceptions,  such 
as  those  indicated,  the  multiplication  of  our  parasitic  and  predaceous 
species  on  the  line  of  the  first  method  is  practically  beyond  our  control. 

It  is  quite  different  in  the  second  method  of  dealing  with  beneficial 
insects,  for  here  man  has  an  opportunity  of  doing  some  very  effective 
work,  and  it  is  only  within  comparatively  recent  years  that  the  impor- 
tance of  this  particular  phase  of  the  subject  has  been  fully  realized.  The 
Rev.  C.  J.  S.  Bethune,  of  Canada,  was  probably  the  first  entomologist 
to  suggest,  in  one  of  the  earlier  volumes  of  the  Canadian  Farmer,  the 
importation  of  the  European  parasites  of  the  Wheat  Midge  (Diplosis 
t t-it id)  into  America,  on  the  supposition  that  this  cosmopolitan  species 
might  thus  be  kept  in  check  on  this  continent  to  the  same  extent  that 
it  was  in  Europe.  So  far  as  I  am  aware,  the  attempt  was  never 
actually  made,  and  though  some  subsequent  correspondence  was 
entered  into  between  Fitch  and  Curtis,  and  later  between  Walsh  and 
some  of  his  English  friends,  nothing  tangible  resulted.  The  matter 
was,  in  fact,  never  seriously  studied  with  this  purpose  in  view. 

The  importance  of  this  phase  of  the  subject  was  early  forced  upon  my 
attention,  as  it  was  upon  that  of  others,  and  is  frequently  referred  to  in 
my  earlier  writings.  Thus,  in  1869-'70,  in  studying  the  parasites  of  the 
Plum  Curculio,  it  became  evident  that  they  were  of  such  a  nature  that 
they  could  easily  be  transported  from  one  locality  to  another,  and  I 
distributed  from  Kirkwood,  Mo.,  Siyalphus  curculionis  Fitch  and  Pori- 
zon  conotraeheli  Kiley  to  several  correspondents  in  other  parts  of  the 
State.  1  also  urged  a  similar  course  with  regard  to  some  of  the  para- 
sites of  the  Coccidie,  which  it  happens  may  be  easily  transported  from 


133 

one  place  to  another  in  their  undeveloped  or  adolescent  stages.*  Le 
Baron,  in  his  studies  of  the  Oyster-shell  Bark-Louse  of  the  Apple  and  one 
of  its  parasites  (Aplielinus  mytilaspidis),  transported  scale-covered  twigs 
during  winter  from  Geneva,  111.,  to  Galena,  111.,  with  beneficial  results. 
The  experiment  was  conducted  on  a  small  scale,  but  the  parasites 
issued  and  became  domiciled  in  t*heir  new  locality,  thus  proving  the 
practicability  of  his  scheme.  In  neither  my  own  experiments  nor  in  Le 
Baron's,  however,  was  sufficiently  thorough  examination  made  to  prove 
that  the  parasites  did  not  already  exist  in  the  localities  in  which  they 
were  colonized. 

Planchon  and  myself  introduced  Tyroglyphus  phylloxerce  from  America 
into  France  in  1873,t  and  it  became  fully  established,  as  subsequent 
correspondence  and  observation  showed.  In  1874  efforts  were  made 
to  send  over  from  England  to  New  Zealand  certain  Aphid  parasites  to 
check  the  alarming  increase  of  those  plant  pests  there,  and  while  I  have 
no  records  at  hand  to  show  with  what  success,  the  later  successful  intro- 
duction of  bumblebees  to  the  latter  country  to  fertilize  the  red  clover 
is  well-known  history.  In  his  report  upon  the  parasites  of  Coecida3  in 
the  Annual  Keport  of  the  Department  of  Agriculture  for  1880,  Mr. 
Howard  gave  the  subject  some  theoretical  attention  and  elaborated 
upon  the  ease  with  which  Coccid  parasites  could  be  transported  from 
one  part  of  the  country  to  another  during  winter.  He  suggested  the 
experiment  of  transporting  Dilophogaster  calif ornica  from  the  Pacific 
coast  to  certain  of  the  Southeastern  States,  where  it  might  be  expected  to 
prey  upon  certain  large  species  of  Lecanium.  In  1883,  after  previous 
futile  attempts  by  myself  and  Mr.  Otto  Lugger,  and  with  the  assistance 
of  G.  C.  Bignell,  esq.,  of  Plymouth,  England,  the  living  cocoons  of 
Microgaster  glomeratus,  a  common  European  parasite  of  Pieris  rapce, 
were  successfully  imported  by  the  Department  and  the  colonization  of 
the  species  was  established,  not  only  in  the  District  of  Columbia,  but 
in  Iowa,  Nebraska,  and  Missouri,  as  specimens  were  simultaneously 
sent  to  the  agents  of  the  Division  in  those  States.f  It  has  become 
so  widely  distributed  since  then  as  to  lead  to  the  inference  that 
it  must  have  been  previously  introduced  at  some  other  points,  though 
the  spread  of  an  introduced  species,  even  when  introduced  at  a  single 
point,  is  often  so  rapid  that  it  surprises  us,  especially  of  a  species 
that  is  winged,  as  evidenced  by  the  spread  of  the  Horn  Fly  (Hcemato- 
Ma  serrata)  over  the  whole  eastern  United  States  in  about  four  years. 
Later,  in  1891,  with  the  aid  of  Mr.  Fred.  Enock,  of  London,  a  success- 
ful effort  was  made  to  introduce  into  this  country  from  England  an 
important  Chalcid  parasite  of  the  Hessian  Fly,  Entedon  epigonus  Walker 
(Semiotellus  nigripes  Lind.).  The  details  of  this  experiment  will  be 


*Tliird  Rep.,  Ins.  Mo.,  1870,  p.  29;  Fifth  Rep.,  do.,  1873,  p.  90. 

t  Sixth  Report,  Ins.  Mo.,  1874,  p.  55. 

t  Report  of  the  Etomologist  in  Rep.  U.  S.  Dept.  Agric.  for  1884,  p.  323. 


134 

found  in  my  published  writings,  especially  in  my  report  as  U.  S.  Ento- 
mologist for  1891,  and  it  is  only  necessary  to  state  at  this  time  that 
parasitized  paparia  of  the  Hessian  Fly  were  received  in  large  numbers 
and  distributed  to  various  points,  and  placed  in  the  care  of  competent 
observers  in  Illinois,  Indiana,  Michigan,  and  Canada.  The  results  so 
far  have  not  been  marked,  and  but  one  positive  report  as  to  the  accli- 
mation of  the  parasite  has  been  received,  viz,  from  Prof.  S.  A.  Forbes, 
of  Champaign,  111.  I  am  of  the  opinion,  however,  that  the  lack  of 
evidence  from  other  points  is  due  almost  entirely  to  lack  of  proper  exam- 
ination, and  I  have  every  hope  that  the  species  will  before  long  be  found 
to  have  obtained  a  secure  foothold  at  all  of  the  several  points  of  intro- 
duction. It  is  a  very  difficult  matter  to  ascertain  the  existence  of  a 
parasite  of  this  minute  size,  except  when  it  occurs  in  great  numbers. 
It  requires  an  eye  trained  not  only  to  the  examination  of  these  minute 
creatures,  but  one  familiar  with  the  allied  imported  species  and  native 
species.  The  reason  for  attempting  the  introduction  of  this  particular 
species  was  simply  that  in  England  it  was  found  to  be  far  more  abun- 
dant and  far  more  beneficial  than  any  of  our  native  species  have  so  far 
proved. 

The  present  year  I  have  become  interested  in  the  matter  of  the 
importation  of  a  predaceous  Noctuid  (Erastria  scitula)  which  preys  upon 
the  Black  Scale  (Lecanium  olece)  in  south  Europe  and  helps  materially 
to  keep  it  in  check.  With  the  help  of  Prof.  H.  Kouzaud,  of  Montpel- 
lier,  France,  who  has  studied  the  habits  of  this  insect  with  extreme 
care,  I  hope  to  establish  it  in  southern  California,  where  the  climatic 
conditions  are  sufficiently  close  to  those  of  south  Europe,  and  where 
the  Black  Scale  does  great  damage  to  olive  orchards  and  to  oleander 
trees,  and  also  affects  less  seriously  the  Orange  and  Lemon.  The  Black 
Scale  has  already  an  important  enemy  in  California  in  the  shape  of  the 
Dilophogaster  above  mentioned,  but  the  latter  is  only  two-brooded,  and 
the  scale  insect,  multiplying  more  rapidly,  outstrips  it  in  the  race  for 
maturity.  The  Erastria,  on  the  contrary,  passes  through  five  or  six  gen- 
erations in  the  course  of  a  summer,  and,  as  it  is  purely  predaceous,  it 
will,  I  believe,  prove  a  most  useful  auxiliary  against  the  Black  Scale, 
especially  if  brought  over  without  its  parasites. 

So  far  I  have  spoken  only  of  the  insects  which  have  been  imported 
into  this  country,  but  some  effort  has  also  been  made  in  the  opposite 
direction.  Thus  we  have  endeavored  (and  with  some  success)  to  return 
the  service  done  us  by  sending  to  Australia  and  New  Zealand  some  of 
our  predatory  Coleoptera,  some  of  the  Pacific  coast  parasites  of  the 
Codling  Moth,  and  a  species  of  the  interesting  genus  Eaphidia,  which 
also  preys  upon  the  Codling  Moth. 

In  1887  and  1888  the  now  well-known  importation  of  Vedalia  cardi- 
nalis  from  Australia  and  New  Zealand  to  California,  to  prey  upon 
leery  a  purchasi,  was  successfully  carried  out.  The  history  of  this 
striking  example  of  the  beneficial  results  that  may,  in  exceptional 


135 

cases,  flow  from  intelligent  effort  in  this  direction,  is  now  sufficiently 
well  known  to  American  economic  entomologists;  but  anticipating  that 
we  shall  have  foreign  delegates  among  us,  and  that  our  proceedings 
will  be  published  more  widely  than  usual,  it  will,  perhaps,  be  wise  to 
give  the  salient  historical  facts  in  the  case,  even  at  the  risk  of  some 
repetition  of  what  has  been  already  published.  In  doing  this  the 
indulgence  of  the  society  is  craved  for  the  prominence  of  my  own  part 
in  the  work,  rendered  necessary  by  the  disposition  in  some  quarters  to 
distort  the  facts. 

The  Fluted  Scale,  otherwise  known  as  the  White  or  Cottony-cushion 
Scale  (Icerya  purchasi  Maskell),  is  one  of  the  largest  species  of  its 
family  (Coccida3),  and  up  to  1888  had  done  immense  injury  to  the  orange 
groves  and  to  many  other  trees  and  shrubs  of  Southern  California. 
From  Australia,  its  original  home,  it  had  been  imported  into  Xew 
Zealand,  South  Africa,  and  California,  the  evidence  pointing  to  its 
introduction  into  California  about  1868,  and,  probably,  upon  Acacia 
latijolia. 

In  my  annual  report  as  U.  S.  Entomologist  for  1886  will  be  found  a 
full  characterization  of  the  species  in  all  its  stages;  but  the  three 
characteristics  which  most  concern  the  practical  man,  and  which  make 
it  one  of  the  most  difficult  species  to  contend  with,  are  its  ability  to  sur- 
vive for  long  periods  without  food,  to  thrive  upon  a  great  variety  of 
plants,  and  to  move  about  throughout  most  of  its  life. 

The  injuries  of  this  insect,  notwithstanding  the  efforts  to  check  it, 
kept  on  increasing,  and  some  ten  years  ago  I  felt  that  the  work  of  this 
particular  species  and  of  others  which  seriously  affected  the  fruit- 
growing interests  of  Southern  California  justified  the  establishment  of 
agencies  there.  Up  to  this  time  no  special  entomological  effort  had  been 
made  by  the  Government  on  behalf  of  the  fruit-growers  of  the  Pacific 
coast.  Through  agents  stationed,  the  one  at  Los  Angeles,  the  other 
at  Alameda,  a  course  of  elaborate  experiments  was  undertaken  as  to 
the  best  means  of  treating  the  insects  affecting  the  Orange  there,  and 
more  particularly  this  Fluted  or  Cottony-cushion  Scale.  During  the 
progress  of  these  investigations,  however,  the  fact  impressed  itself 
upon  my  mind  that  we  had  here  an  excellent  opportunity  of  calling  to 
our  aid  its  own  natural  enemies,  for  while  there  were  some  doubts  as 
to  the  origin  of  Icerya,  the  question  was  finally  settled  to  my  own  sat- 
isfaction that  it  was  of  Australian  origin,  and  that  in  its  native  home 
it  was  not  a  serious  pest,  but  was  kept  subdued  by  natural  checks. 
These  facts  were  not  positively  ascertained  without  a  good  deal  of 
correspondence  and  investigation,  involving,  in  fact,  a  trip  to  France, 
as  has  been  set  forth  in  my  published  writings  upon  the  subject. 

In  my  report  as  U.  S.  Entomologist  for  1886,  in  an  address  before 

the  State  Board  of  Horticulture  at  Riverside,  California,  in  1887; 

in  a  paper  before  the  Philosophical  Society  of  Washington  in  the 

winter  of  1888,  and  elsewhere,  I  urged,  with  all  the  force  at  my  com- 

9052— No.  2 6 


13f> 

raand,  the  advisability  of  endeavoring  to  introduce  the  natural  enemies 
which  were  known  to  keep  it  in  check  in  Australia.  Certain  indige- 
nous species  had  been  discovered  preying  upon  it  in  California,  and  I 
expressed  the  belief  that,  as  they  increased,  the  fruit-growers  would 
get  more  and  more  relief  from  the  Icerya;  but  I  also  urged  that  there 
was  much  more  chance  of  success  from  those  which  keep  it  in  check  in 
its  native  home,  and  which  were  not  imported  with  it  to  the  countries 
of  its  introduction.  The  case  was  exceptional,  and  the  attempt  thus 
urged  gave  every  promise  of  a  rich  reward.  Efforts  were  made  to 
introduce  some  of  these  natural  enemies  through  correspondence, 
especially  with  the  late  F.  S.  Crawford,  of  Adelaide,  with  what  ulti- 
mate results  the  subsequent  success  of  Vedalia  forever  rendered 
uncertain. 

The  Hon.  H.  H.  Markham,  present  Governor  of  California,  was  at 
that  time  a  Representative  in  Congress,  and  through  him  chiefly,  but 
also  through  others,  I  urged  upon  Congress  the  desirability  of  sending 
some  one  to  Australia  to  make  a  thorough  study  of  the  subject  with  a 
view  of  introducing  those  natural  enemies.  Again,  in  the  winter  of 
18S7-?88  appeals  were  made  to  Congress,  not  only  of  a  personal  nature, 
but  through  memorials  from  various  societies  in  California,  for  an  appro- 
priation to  send  one  or  two  men  to  Australia  to  collect  and  increase 
these  natural  enemies.  Congress,  however,  failed  to  make  any  specific 
appropriation,  and  also  failed  to  remove  the  restriction  in  the  appro- 
priation to  the  Division  of  Entomology  which  limited  traveling  expenses 
to  the  United  States  and  prevented  independent  action  of  the  Depart- 
ment of  Agriculture.  It  happened,  however,  that  about  this  time  an 
appropriation  was  made  and  a  commission  created  to  represent  the  United 
States  at  the  Melbourne  Exposition,  and,  with  the  appreciative  aid  and 
sympathy  of  the  Hon.  Norman  J.  Colman,  Commissioner  of  Agriculture, 
I  took  active  steps  to  gain  the  cooperation  of  the  Secretary  of  State  in 
my  pet  scheme,  and  by  an  arrangement  with  the  Department  of  State, 
accepted  by  the  commissioner  to  said  Exposition,  Hon.  Frank  McCoppin, 
the  Department  of  Agriculture  was  finally  enabled  to  send  to  Australia 
two  agents  of  the  Division  of  Entomology,  one  of  them  to  be  under  my 
instructions,  and  the  expenses  of  both,  within  the  sum  of  $2,000,  to  be 
paid  out  of  the  appropriation  for  the  aforesaid  Exposition. 

It  was  thus  that  Mr.  Albert  Koebele,  in  the  fall  of  1888,  was  sent  to 
Australia  for  this  special  purpose.  The  history  of  Mr.  Koebele's  efforts 
has  been  detailed  from  time  to  time  in  Government  publications  and  in 
the  press,  especially  that  of  California.  It  suffices  to  state  that  a  num- 
ber of  living  enemies,  both  parasitic  and  predaceous,  were  successfully 
imported,  but  that  one  of  them,  Vedalia  cardinalis,  proved  so  effective 
as  to  throw  the  others  entirely  into  the  shade  and  render  their  services 
really  unnecessary.  It  has,  so  far,  not  been  known  to  prey  upon  any 
other  insect,  and  it  breeds  with  surprising  rapidity,  occupying  less  than 
thirty  days  from  the  laying  of  the  eggs  until  the  adults  again  appear. 


137 

These  facts  account  for  its  exceptionally  rapid  work,  for  in  point  of  fact, 
within  a  year  and  a  half  of  its  first  introduction,  it  had  practically 
cleared  off  the  Fluted  Scale  throughout  the  infested  region.  The  expres- 
sions of  two  well-known  people  may  be  quoted  here  to  illustrate  the  gen- 
eral verdict.  Prof.  W.  A.  Henry,  Director  of  the  Wisconsin  Agricul- 
ture Experiment  Station,  who  visited  California  in  1889,  reported  that 
the  work  of  Vedalia  was  u  the  finest  illustration  possible  of  the  value 
of  the  Department  to  give  the  people  aid  in  time  of  distress.  And  the 
distress  was  very  great  indeed."  Mr.  William  F.  Channing,  of  Pasa- 
dena, son  of  the  eminent  Unitarian  divine,  wrote  two  years  later: 

We  owe  to  the  Agricultural  Department  the  rescue  of  our  orange  culture  by  the 
importation  of  the  Australian  ladybird,  Vedalia  cardlnalis. 

The  white  scales  were  incrusting  our  orange  trees  with  a  hideous  leprosy.  They 
spread  with  wonderful  rapidity  and  would  have  made  citrus  growth  on  the  whole 
North  American  continent  impossible  within  a  few  years.  It  took  the  Vedalia, 
where  introduced,  only  a  few  weeks  absolutely  to  clean  out  the  white  scale.  The 
deliverance  was  more  like  a  miracle  than  anything  I  have  ever  seen.  In  the  spring 
of  1889  I  had  abandoned  my  young  Washington  navel  orange  trees  as  irrecoverable. 
Those  same  trees  bore  from  two  to  three  boxes  of  oranges  apiece  at  the  end  of  the 
season  (or  winter  and  spring  of  1890).  The  consequence  of  the  deliverance  is  that 
many  hundreds  of  thousands  of  orange  trees  (navels  almost  exclusively)  have  been 
set  out  in  southern  California  this  last  spring. 

In  other  words,  the  victory  over  the  scale  was  complete  and  will  prac- 
tically remain  so.  The  history  of  the  introduction  of  this  pest,  its 
spread  for  upwards  of  twenty  years,  and  the  discouragement  which 
resulted,  the  numerous  experiments  which  were  made  to  overcome  the 
insect,  and  its  final  reduction  to  unimportant  numbers  by  means  of  an 
apparently  insignificant  little  beetle  imported  for  the  purpose  from 
Australia  will  always  remain  one  of  the  most  interesting  stories  in  the 
records  of  practical  entomology. 

The  Vedalia  has  since  been  successfully  colonized  at  the  Cape  of 
Good  Hope  and  in  Egypt,  and  has  produced  the  same  results  in  each 
case.  In  Egypt  the  Vedalia  was  introduced  to  prey  upon  an  allied 
species  of  leery  a  ( I.  cegyptiacum,  Douglas).  We  hope  soon  to  be  able  to 
send  the  same  insect  to  India,  where  it  has  recently  transpired  that 
Icerya  cegyptiacum  occurs,  while  recent  information  received  from  Phra 
Suriya,  royal  commissioner  of  Siam  at  Chicago,  would  indicate  that  its 
introduction  into  Siam  for  the  same  or  a  closely  allied  insect  will  be 
desirable  in  the  near  future. 

In  fact,  the  success  of  the  experiment  was  so  striking  and  so  impor- 
tant, and  resulted  in  the  saving  to  California  of  an  industry  of  so  great 
a  money  value,  that  it  has  given  rise,  not  only  in  the  popular  mind  but 
in  the  minds  of  a  certain  class  of  entomologists  also,  to  the  idea  that 
remedial  work  against  injurious  insects  should  be  concentrated  upon 
this  one  line  of  action,  and  that  our  best  hope  for  their  destruction 
lies  with  the  parasitic  and  predaceous  species,  not  to  mention  fungus  and 
bacterial  diseases.  From  an  extreme  of  comparative  incredulity  the 


138 

farmer  and  fruit-grower  have  gone,  perhaps,  to  the  other  extreme  of 
too  great  faith.  The  case  of  leery  a  and  Vedalia,  as  I  have  frequently 
pointed  out,  was  exceptional  and  one  which  can  not  easily  be  repeated* 

One  of  the  humorous  phases  of  the  Vedalia  experiment  is,  that  the 
wide  newspaper  circulation  of  the  facts — not  always  most  accurately 
set  forth — has  brought  me  communications  from  all  parts  of  the  world 
asking  for  supplies  of  the  renowned  little  Ladybird  for  use  against 
injurious  insects  of  every  kind  and  description,  the  inquiries  being 
made,  of  course,  under  a  misapprehension  of  the  facts. 

While  this  California  experience  thus  affords  one  of  the  most  striking 
illustrations  of  what  may  be  accomplished  under  exceptional  circum- 
stances by  the  second  method  of  utilizing  beneficial  insects,  we  can 
hardly  expect  to  succeed  in  accomplishing  much  good  in  this  direction 
without  a  full  knowledge  of  all  the  ascertainable  facts  in  the  case  and 
a  due  appreciation  of  the  profounder  laws  of  nature,  and  particularly  of 
the  interrelations  of  organisms.  Year  in  and  year  out,  with  the  condi- 
tions of  life  unchanged  by  man's  actions,  the  relations  between  the 
plant-feeder  and  the  predaceous  and  parasitic  species  of  its  own  class 
remain  substantially  the  same,  whatever  the  fluctuations  between  them 
for  any  given  year.  This  is  a  necessary  result  in  the  economy  of 
nature ;  for  the  ascendancy  of  one  or  the  other  of  the  opposing  forces 
involves  a  corresponding  fluctuation  on  the  decreasing  side,  and  there 
is  a  necessary  relation  between  the  plant-feeder  and  its  enemies,  which, 
normally,  must  be  to  the  slight  advantage  of  the  former  and  only 
exceptionally  to  the  great  advantage  of  the  latter. 

This  law  is  recognized  by  all  close  students  of  nature,  and  has  often 
been  illustrated  and  insisted  upon  by  entomologists  in  particular,  as 
the  most  graphic  exemplifications  of  it  occur  in  insect  life,  in  which 
fecundity  is  such  that  the  balance  is  regained  with  marvelous  rapidity, 
even  after  approximate  annihilation  of  any  particular  species.  But  it 
is  doubtful  whether  another  equally  logical  deduction  from  the  prev- 
alence of  this  law  has  been  sufficiently  recognized  by  us,  and  this  is, 
that  our  artificial  insecticide  methods  have  little  or  no  effect  upon  the 
multiplication  of  an  injurious  species,  except  for  the  particular  occa- 
sion which  calls  them  forth,  and  that  occasions  often  arise  when  it  were 
wiser  to  refrain  from  the  use  of  such  insectides  and  to  leave  the  field 
to  the  parasitic  and  predaceous  forms. 

It  is  generally  when  a  particular  injurious  insect  has  reached  the 
zenith  of  its  increase  and  has  accomplished  its  greatest  harm  that  the 
farmer  is  led  to  bestir  himself  to  suppress  it,  and  yet  it  is  equally  true 
that  it  is  just  at  this  time  that  nature  is  about  to  relieve  him  in  strik- 
ing the  balance  by  checks  which  are  violent  and  effective  in  proportion 
to  the  exceptional  increase  of  and  consequent  exceptional  injury  done 
by  the  injurious  species.  Now  the  insecticide  method  of  routing  this 
last,  under  such  circumstances,  too  often  involves,  also,  the  destruc- 
tion of  the  parasitic  and  predaceous  species,  and  does  more  harm  than 


139 

good.  This  is  particularly  true  of  those  of  our  Coccidae  and  Aphi. 
didae  and  those  of  our  Lepidopterous  larva}  which  have  numerous  natu- 
ral enemies  of  their  own  class;  and  it  not  only  emphasizes  the  impor- 
tance of  preventive  measures,  which  we  are  all  agreed  to  urge  for  other- 
cogent  reasons,  and  which  do  not  to  the  same  extent  destroy  the  para- 
sites, but  it  affords  another  explanation  of  the  reason  why  the  fight  with 
insecticides  must  be  kept  up  year  after  year,  and  has  little  cumulative 
value. 

But  the  problem  of  the  wise  encouragement  and  employment  of  the 
natural  enemies  of  injurious  insects  in  their  own  class  is  yet  more  com- 
plicated. The  general  laws  governing  the  interaction  of  organisms  are 
such  that  we  can  only  in  very  exceptional  cases  derive  benefit  by 
interference  with  them.  The  indigenous  enemies  of  an  indigenous  phy- 
tophagous species  will,  cceteris  paribus,  be  better  qualified  to  keep  it 
in  check  than  some  newly  introduced  competitor  from  a  foreign  coun- 
try, and  the  peculiar  circumstances  must  decide  in  each  case  the 
advisability  of  the  introduction.  The  multiplication  of  the  foreigner 
will  too  often  involve  the  decrease  of  some  indigene.  If  a  certain  phy- 
tophage  is  generally  disastrous  in  one  section  and  innocuous  in  another 
by  virtue  of  some  particular  enemy  it  will  be  safe  to  transfer  and 
encourage  such  enemy,  and  this  is  particularly  true  when  the  phy- 
tophage  is  a  foreigner  and  has  been  brought  over  without  the  enemy 
which  subdues  it  in  its  native  home.  Icerya  had  some  enemies  in  Cali- 
fornia, presumably  American,  but  they  were  not  equal  to  the  task 
of  subduing  it.  Yedalia,  in  the  Icerya's  native  home,  Australia,  was 
equal  to  the  task  and  maintained  the  same  superiority  over  all  others 
when  brought  to  America.  The  genus  was  new  to  the  country  and 
the  species  had  exceptionally  advantageous  attributes.  But  there  is 
very  little  to  be  hoped  from  the  miscellaneous  introduction  of  preda- 
ceous  or  parasitic  insects  for  the  suppression  of  a  phytophage  which 
they  do  not  suppress  in  their  native  home  or  in  the  country  from  which 
they  are  brought. 

The  results  of  the  introduction  by  Mr.  A.  D.  Hopkins  of  Clermformi- 
carius  to  contend  with  the  Scolytids  which  were  ruining  the  West  Vir- 
ginia pines  were  doubtful,  for  the  reason  that  indigenous  species  of  the 
genus  were  already  at  work  in  America.  Yet  the  experiment  was  safe 
and  desirable,  because  the  European  Olerus  is  more  active  and  more 
seemingly  effective  than  our  indigenes.  The  Gypsy  Moth  was  evidently 
introduced  into  Massachusetts  without  its  European  natural  enemies, 
and  as  in  some  parts  of  Europe  it  is  often  locally  checked  by  such  natural 
enemies,  a  great  number  of  which  are  known,  a  proper  study  of  them 
and  the  introduction  of  the  most  effective  could  result  in  no  possible 
harm  and  might  be  productive  of  lasting  good.  Such  a  course  was 
advised  by  me  at  a  conference  upon  the  subject  held  in  the  rooms  of 
the  State  Board  of  Agriculture,  Boston,  March  4,  1891,*  and  in  corre 


INSECT  LIFE,  in,  p.  369,  ff. 


140  i1;  \  Y 

spondence  with  the  Secretary  of  the  Board  I,i  nHtli-T  <>f 
should  we  expect  the  predaceous  or  parasitic  forms  to  subdue  their 
hosts  more  effectually  in  America  than  they  do  in  Europe,  except  in  so 
far  as  they  were  relieved,  in  the  introduction  into  America,  of  whatever 
enemies  they  possessed  in  their  native  home. 

There  are  two  other  laws  which  it  is  worth  while  to  consider  in  this 
connection.  One  is,  that  while  a  plant-feeder's  natural  enemies  are  <  pt 
to  cause  its  excessive  abundance  to  be  followed  by  a  corresponding 
decrease,  yet  this  alternation  of  excessive  abundance  and  excessive 
scarcity  will  often  be  produced  irrespective  of  such  natural  checks.  An 
injurious  insect  which  has  been  on  the  destructive  march  for  a  period 
•of  years  will  often  come  to  a  sudden  halt,  and  a  period  of  relative,  and 
sometimes  complete,  immunity  from  injury  will  follow.  This  may  result 
from  climatic  conditions,  but  more  often  it  is  a  consequence  of  disease, 
debility,  and  want  of  proper  nutrition,  which  are  necessary  corollaries 
of  undue  multiplication.  Frequently,  therefore,  it  may  be  inaccurate 
and  misleading  to  attribute  the  disappearance  of  a  particular  injurious 
species  to  some  parasitic  or  predaceous  species  which  has  been  let 
loose  upon  it,  and  nothing  but  the  most  accurate  observation  will 
determine  the  truth  in  such  cases.  The  past  year  furnished  a  very 
graphic  illustration  in  point.  Throughout  Virginia  and  West  Virginia, 
where  the  spruce  pines  have  for  some  years  suffered  so  severely  from 
the  destructive  work  of  Dendroctonus  frontalis,  not  a  single  living 
specimen  of  the  beetle  has  been  found  during  the  present  year.  This 
has  been  observed  by  every  one  who  has  investigated  the  subject,  and 
particularly  by  several  correspondents  who  have  written  to  me;  by  Mr. 
E.  A.  Schwarz,  who  was  commissioned  to  investigate  the  facts,  and  by 
Mr.  Hopkins,  who  has  made  the  study  of  the  subject  a  specialty. 

The  clearest  explanation  of  this  sudden  change  is  that  the  species 
was  practically  killed  out  by  the  exceptionally  severe  cold  of  last 
winter,  since  such  was  the  case  with  several  other  insects.  Now,  fol- 
lowing so  closely  on  the  introduction  by  Mr.  Hopkins  of  Glerus  formi- 
cariusj  how  easy  it  would  have  been  to  attribute  the  sudden  decrease 
to  the  work  of  the  introduced  Olerus  had  not  the  decrease  been  so 
general  and  extensive  as  absolutely  to  preclude  any  such  possibility. 
In  like  manner  a  certain  Scale  Insect  (Aspidiotus  tenelricosus)  had 
become  exceedingly  destructive  to  the  Soft  Maples  in  the  city  of  Wash- 
ington last  year,  whereas  the  present  year  it  is  almost  entirely  killed 
off,  evidently  by  the  same  exceptional  cold.  Many  of  the  affected 
trees  were  painted  with  whitewash,  with  a  view  of  destroying  the 
Aspidiotus,  and  the  death  of  this  last  might  have  been  attributed  to 
the  treatment  (and  naturally  would  be  by  those  employing  it)  were  it 
not  that  the  same  result  was  equally  noticeable  on  the  trees  not 
treated.  Reports  from  southern  California  would  indicate  that  the  Red 
Scale  (Aspidiotus  aurantii)  is,  in  many  orchards,  losing  its  destructive. 
ness  through  agencies  other  than  its  insect  enemies,  and  in  this  case 
the  facts  are  particularly  interesting  because  of  the  ease  with  which 


141 

its*  (iisabpeariiDce  may  be  attributed  to  some  of  the  recent  introduc- 
tions from  Australia.' 

The  other  law  that  is  worth  considering  in  this  connection  is  that 
experience  has  shown  that,  as  a  rule,  the  animals  and  plants  of  what 
is  known  as  the  "Old"  World — i.  e.,  of  Europe  and  Asia — when  intro- 
duced into  North  America  have  shown  a  greater  power  of  multiplica- 
tion than  the  indigenous  species,  and  in  a  large  number  of  instances 
have  taken  the  place  of  the  native  forms,  which  have  not  been  able  to 
compete  with  them  in  the  struggle  for  existence.  The  converse  prop- 
osition holds  equally  true,  viz :  that  our  species  when  taken  to  Europe 
do  not  hold  their  own  against  the  European  indegenes.  This  is  still  more 
true  of  the  species  introduced  from  the  Old  World,  as  well  as  from 
America,  into  Australia,  where  the  advantage  of  the  introduced  forms, 
as  compared  with  the  indigenous,  has  been  in  many  cases  still  more 
marked.  All  other  things  being  equal,  therefore,  we  should  expect  the 
species  which  are  beneficial  in  Australia  to  be  less  so  when  brought  to 
this  country,  a  deduction  which  brings  out  still  more  clearly  the 
exceptional  nature  of  the  case  of  Vedalia  and  Icerya,  just  as  there  are 
some  notable  exceptions,  as  in  the  case  of  the  Grape  Phylloxera,  in  the 
introductions  between  Europe  and  America. 

There  are  some  instances  in  which  there  can  be  no  doubt  whatever 
as  to  the  good  which  would  flow  from  the  introduction  of  beneficial 
species,  and  an  illustration  is  afforded  in  the  Capri-fig  insect,  Blastophaga, 
psenes.  There  can  be  no  question  as  to  the  good  which  would  result 
from  the  introduction  of  this  species  from  Smyrna  into  those  sections 
of  California  where  the  Smyrna  fig  is  grown  without  its  intervention 
and  there  are  other  similar  instances  which  promise  well  and  involve 
no  risk.  But  I  have  said  enough  to  show  that  the  successful  utiliza- 
tion of  beneficial  insects  is  by  no  means  a  simple  matter  and  that  dis- 
criminating knowledge  is  required  to  insure  success  or  prevent  dis- 
aster, especially  in  the  second  category  dealt  with  in  this  paper.  The 
danger  attending  introductions  of  beneficial  species  by  unconsciously 
accompanying  them  with  injurious  forms,  or  by  failure  to  appreciate 
the  facts  here  set  forth,  is  well  illustrated  by  the  introduction  to 
Europe  of  our  Peronospora  mticola,  of  the  English  Sparrow  to  America, 
and  of  the  Mongoose  to  Jamaica.  Wherever  the  importance  of  the 
matter  leads  to  legislation,  what  are  denominated  " political"  methods 
are  apt  either  to  control  or  in  some  way  influence  the  resulting  efforts — 
too  often  with  unfortunate  consequences.  We  should,  as  economic 
entomologists,  be  on  the  alert  for  special  cases  where  the  introduction 
or  dissemination  of  beneficial  species  promises  good  results,  and  do 
our  best  to  encourage  an  intelligent  public  appreciation  of  such  special 
cases,  while  discouraging  all  that  is  of  a  sensational  nature,  as  likely 
to  mislead  and  ultimately  do  our  profession  more  harm  than  good. 


GENERAL  LIBRARY 
UNIVERSITY  OF  CALIFORNIA— BERKELEY 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

This  book  is  due  on  the  last  date  stamped  below,  or  on  the 

date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 


ENTOM 


OLOGY  LIBRARY 


JUL22'82 


LD  21-100m-l,'54(1887sl6)476 


